The advantage of raising a vehicle on tubular leg posts for row crop cultivation is taught by Thomsen U.S. Pat. No. 2,749,137 and of combining steering and drive mechanisms in such tubular leg posts is taught by Kosman U.S. Pat. No. 2,994,392. In addition, a means of partially isolating a vehicle from torsional stresses resulting from uneven terrain is taught by Bishop U.S. Pat. No. 3,266,815. Further examples of the prior art are U.S. Pat. No. 3,366,398 (Mulholland); U.S. Pat. No. 4,566,553 (McCutcheon) and U.S. Pat. No. 812,037 (Hanson).
The vehicles of the prior art have suffered from a number of disadvantages. For example, the frames of U.S. Pat. Nos. 3,266,815 and 3,366,398 support platforms which are substantially elevated above the frame so that the vehicles are not inherently stable. Furthermore, those prior art machines which are self-propelled generally have rigid support frames and an overly complicated drive arrangement.